The present invention relates generally to microcatheters used in the field of interventional radiology. More particularly, this invention pertains to microcatheters used in endovascular procedures for diagnostic imaging and therapy of vascular pathology.
Since the 1980's, microcatheter technology has advanced to become commonplace in the treatment of vascular lesions of the central nervous system. Microcatheters have been used to treat cerebral aneurysms, fistulas, and arterial venous malformations, for example, by occluding the parent vessel or the pathologic vascular abnormality through an endovascular approach, using selective deposition of coils, particles, or liquid adhesives. The microcatheter can also be used to deliver chemotherapeutic agents to spinal, head and neck, or intracranial malignancies. Microcatheters are used as well to deliver agents to open occluded vasculature, including agents to dissolve clots. Balloon microcatheters are used to open vessels narrowed due to atherosclerosis.
As used in the prior art, a microcatheter is advanced from a femoral puncture through the lumen of a guiding catheter which terminates in a carotid or vertebral artery. The microcatheter is advanced beyond the guiding catheter using one of two known techniques. One such prior art technique is directing a guide wire through the lumen of the microcatheter which has varying degrees of tip-shape, torqueability, stiffness and external coating. A second prior art method is a flow-directed technique in which the microcatheter is extremely flexible and is carried by blood flow to the lesion, assisted by of injections of saline or contrast media through the flow directed microcatheter.
Each of the primary conventional methodologies for delivering a microcatheter has drawbacks. The guidewire directed microcatheter involves the risk of puncturing a vessel or aneurysm, which can have devastating hemorrhagic consequences intracranially. With the flow-directed microcatheter, it is frequently difficult to make precise turns and select individual vessels when complex vascular anatomy is encountered. A guidewire cannot be used in the flow-directed microcatheter because of the suppleness of the microcatheter and the significant possibilities of puncturing the wall of the microcatheter with a stiff guidewire. This also prohibits the delivery of coils (used to assist in occlusion) through a flow-directed microcatheter. Thus, only liquid adhesive or tiny particles can be injected through the flow-directed variety of microcatheter for vascular occlusion, the tiny particles usually of insufficient size to achieve the desired vascular occlusion. Conversely, the guide-wire directed microcatheter often times cannot be pushed from the groin over a guidewire through multiple turns in branching intracranial vascularity to reach the desired vessel.
In one prior art attempt at improvement of these techniques, a method has been developed to incorporate a balloon into the tip of a microcatheter to allow the blood flow to carry the distended balloon distally to the desired target vessel. The disadvantage with the balloon technology is that two lumens are required, one for the lumen to deliver the embolic agent, and the second to inflate and deflate the balloon. Alternatively, a calibrated leak balloon can be incorporated in the tip of the microcatheter. This, however, does not allow for directionality and cannot be used with a guidewire.
Thus, it is an object of the present invention to achieve catheterization of high-flow vascular lesions in the head, or elsewhere, using flow-directed as well as guidewire technology and permitting delivery of all embolic agents.